This brain region has been implicated in planning complex
cognitive behaviors, personality expression, decision making and
moderating correct social behavior. The basic activity of this
brain region is considered to be orchestration of thoughts and
actions in accordance with internal goals.

The most typical
psychological term for functions carried out by the
pre-frontal cortex area is
executive function. Executive function relates to abilities
to differentiate among conflicting thoughts, determine good and
bad, better and best, same and different, future consequences of
current activities, working toward a defined goal, prediction of
outcomes, expectation based on actions, and social "control"
(the ability to suppress urges that, if not suppressed, could
lead to socially-unacceptable outcomes).

Many authors have indicated an integral link between a
person's personality and the functions of the prefrontal cortex.

Interconnections

The prefrontal cortex has a high number of interconnections
between both the
brainstem's
Reticular Activating System (RAS) and the
limbic system. As a result, the centers in the prefrontal
cortex depend significantly on high levels of alertness, and
emotional linkages with deeper brain structures related to
control of pleasure, pain, anger, rage, panic, aggression
(fight-flight-freeze responses), and basic sexual responses.

Studies

Perhaps the seminal case in prefrontal cortex function is
that of
Phineas Gage, whose personality may have changed after an
1848 accident destroyed one or both frontal lobes. The standard
presentation (e.g. [2])
is that although Gage retained normal memory, speech and motor
skills, his personality changed radically. He became irritable,
quick-tempered, and impatient, characteristics that he
previously did not exhibit, so that friends described him as "no
longer Gage." And whereas he had previously been a capable and
efficient worker, afterwards he was unable to complete the
multiple tasks that he started. However, careful analysis of
primary evidence shows that descriptions of Gage's psychological
changes are usually exaggerated, the most striking feature being
that changes described years after his death are far more
dramatic than anything reported while he was alive
[3].

Subsequent studies, on patients with prefrontal injuries,
have shown that the patients verbalized what the most
appropriate social responses would be under certain
circumstances, yet, when actually performing, they instead
pursued behavior that is aimed at immediate gratification
despite knowing the longer-term results would be self-defeating.

The interpretation of this data indicates that not only are
skills of comparison and understanding of eventual outcomes
harbored in the prefrontal cortex but the prefrontal cortex
(when functioning correctly) controls the mental option to delay
immediate gratification for a better or more rewarding
longer-term gratification result. This ability to wait for a
reward is one of the key pieces that define optimal executive
function of the human brain.

There is much current research devoted to understanding the
role of the prefrontal cortex in neurological disorders. Many
diseases, such as
schizophrenia,
bipolar disorder and
ADHD, have been related to dysfunction of the prefrontal
cortex, and thus this area of the brain offers the potential for
new treatments of these diseases. Clinical trials have begun
around certain drugs that have been shown to improve prefrontal
cortex function, including
guanfacine which acts through the
alpha-2A adrenergic receptor. A downstream target of this
drug, the
HCN channel, is one of the most recent areas of exploration
in prefrontal cortex pharmacology.[]

Miller and Cohen propose an Integrative Theory of Prefrontal
Cortex Function. The two theorize that “cognitive control stems
from the active maintenance of patterns of activity in the
prefrontal cortex that represents goals and means to achieve
them. They provide bias signals to other brain structures whose
net effect is to guide the flow of activity along neural
pathways that establish the proper mappings between inputs,
internal states, and outputs needed to perform a given task”
(Miller & Cohen, 2001). Essentially the two theorize that the
prefrontal cortex guides the inputs and connections which allows
for cognitive control of our actions.

The prefrontal cortex (PFC) is of significant importance when
top-down processing is needed. Top-down processing by definition
is when behavior is guided by internal states or intentions.
According to the two, “The PFC is critical in situations when
the mappings between sensory inputs, thoughts, and actions
either are weakly established relative to other existing ones or
are rapidly changing”(Miller & Cohen, 2001). An example of this
can be portrayed in the Wisconsin card sort task (WCST).
Subjects engaging in this task are instructed to sort cards
according to the shape, color, or number of symbols appearing on
them. The thought is that any given card can be associated with
a number of actions and no single stimulus-response mapping will
work. Human subjects with PFC damage are able to sort the card
in the initial simple tasks, but unable to do so as the rules of
classification change.

Miller and Cohen conclude that the implications of their
theory can explain how much of a role the PFC has in guiding
control of cognitive actions. In the researchers own words they
claim that “depending on their target of influence,
representations in the PFC can function variously as attentional
templates, rules, or goals by providing top-down bias signals to
other parts of the brain that guide the flow of activity along
the pathways needed to perform a task” (Miller & Cohen, 2001).

Other disorders

In the last few decades,
brain imaging systems have been used to determine brain
region volumes and nerve linkages. Several studies have
indicated that reduced volume and interconnections of the
frontal lobes with other brain regions is observed in those with
schizophrenia, depression, people subjected to repeated
stressors,[4]
suicide victims,[5]
incarcerated criminals, sociopaths, and drug addicts. It is
believed that at least some of the human abilities to feel guilt
or remorse, and to interpret reality, lie in the prefrontal
cortex.[] It is also widely believed that the
size and number of connections in the prefrontal cortex relates
directly to sentience, as the prefrontal cortex in humans
occupies a far larger percentage of the brain than any other
animal. Additionally, as the brain has tripled in size over 5
million years of human evolution, the prefrontal cortex had
increased in size sixfold.